The recent energy crisis brought on a public consciousness of the need for the conservation of energy. As a result the demand for all products and devices used in the building industry and which save energy increased dramatically. One such product is the insulated window. Energy conscious buyers or leasers of new commercial or residential buildings require the installation of insulated windows. Furthermore insulated windows are used whenever windows in older buildings need replacement.
Typically an insulated window comprises two or more window panes of glass or a similar transparent material separated by frame assembly. Side members are mounted around the panes to keep the panes and the frame assembly together.
The frame assembly is necessary to keep the panes parallel to each other and to insure they do not warp. If the panes are not perfectly parallel or straight they look unesthetical to the eye. Furthermore warping of the panes puts undue transversal and longitudinal strain on the panes and causes them to crack or break under the effect of normal wear and tear, temperature variations, and so forth.
Typically frame assemblies are made of tubular members placed end to end and perpendicular to each other to form a rectangle. The size of the rectangle is dictated by the size of the window panes. The members are held together by corner pieces which are adapted to hold the individual members together prior to and during the assembly of the window. These corner pieces are required to be light weight, inexpensive and relatively simple so that they do not extend into the volume defined by the panes and the frame assembly where they would be visible, and do not otherwise interfere with the assembly of the window. At the same time they must be able to hold together the frame members while the assembly is subjected to the normal manufacturing exigencies. For example semi-automated assembly lines have been used for windows in which the frame assembly was transported from one place to another by conveyor belts. It was found that with the prior corner pieces any sudden change in speed or direction of the conveyor belt caused the frame assembly to fall apart because the corner pieces did not function properly.